Conventionally, to form a molded article of a fiber-reinforced composite material with a three-dimensional shape such as a container-like shape using prepreg obtained by impregnating a reinforcing fiber with a matrix resin, in the case the three-dimensional shape is moderately projected or recessed shape with a small curvature, it can be formed easily by pressing and extending the prepreg from both sides by a press die having a desired shape.
For example, in a method of producing a golf club as disclosed in Japanese Patent Application Laid-Open No. 6-98933 (Patent Document 1), when preliminarily molding a portion of ahead of a golf club with a three-dimensional shape, the portion of the head is divided into a plurality of parts and the respective parts are molded by pressing prepreg cut into predetermined shapes. The respective parts of the head preliminarily molded in such a manner and a preliminarily molded shaft are inserted into a hollow molding die, pressure is applied to these preliminarily molded articles from an inner side of the articles to heat and mold them. Consequently, the shaft and the respective parts of the head are joined and united to produce a golf club.
However, in the case where a molded article has an uneven shape with a high curvature, it is inevitable for a method of producing a three-dimensional molded article by press-molding prepreg using a press die that wrinkles are formed by press-molding a sheet-like prepreg on a press die face having similarly an uneven face with a high curvature. Therefore, in the case of molding a three-dimensional shape with a high curvature, partial notches or cutouts are formed previously in prepregs, and the prepregs are laminated and molded in such a manner that end edge parts of the notches or cutouts are laid over so as not to form wrinkles.
For example, in the case of forming a semi-spherical shape, as illustrated in FIG. 10, first prepreg is cut into a circular shape and with a center portion 3a of a circular prepreg 3 being left, a plurality of notches 3b are radially formed at equal intervals, or alternatively, as illustrated in FIG. 11, with a center portion 4a of a circular prepreg 4 left, a plurality of cutouts 4b are radially formed at equal intervals. Successively, with the center portions 3a, 4a of the circular prepreg 3, 4 fitted in a summit part of a press die (a third press die to be described later) 20 having a semispheric projected part 20a as illustrated in FIG. 6 or fitted in the bottom center part of a press die (a fourth press die to be described later) 21 having a semicircular concave part 21a as illustrated in FIG. 7, the prepreg is laminated on the semispheric press die 20 or 21. In this case, the neighboring end edge parts of the notches 3b or cutouts 4b are laid over. Next, the counterpart press die is put on and press-molding is carried out to obtain a molded article with a semispherical shape as a whole.
Conventionally, the step of laying the prepreg on the press die and overlapping the end edge parts of the notches or cutouts is carried out manually in general. Therefore, by the above-mentioned method, a molded article is obtained with quality insufficient in stability and unsatisfactory in the uniformity and productivity as well. Further, at the time of putting the counterpart press die to carry out press-molding, in the case the overlapping of the end edge parts of the notches or cutouts is insufficient or unstable, wrinkling tends to be caused in the end edge parts owing to entrainment of them and also the arrangement of the reinforcing fiber is disordered. Therefore, the above-mentioned method is regarded to be difficult to be employed for producing a molded article required to have a high strength and good appearance.
The invention has been accomplished so as to solve the above-mentioned problems, and an object of the invention is to provide a method of producing a molded article of a fiber-reinforced composite material having a three-dimensional shape by pressing using prepreg cut off in a predetermined shape, which is a method of stably and efficiently producing a molded article of a fiber-reinforced composite material having uniform quality without wrinkles, and to give a preliminarily molded article and a completed molded article by the method.